Tropical Storm DALILA

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TROPICAL STORM DALILA DISCUSSION NUMBER 12
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP072007
200 PM PDT TUE JUL 24 2007
LATEST CONVENTIONAL SATELLITE IMAGERY INDICATES THAT DALILA
CONTINUES TO GRADUALLY STRENGTHEN DESPITE MOST OF THE DEEP
CONVECTION BEING DISPLACED SOUTH OF THE CENTER. THE CURRENT
INTENSITY HAS BEEN INCREASED TO 50 KTS BASED ON A CONSENSUS OF THE
SUBJECTIVE DVORAK ESTIMATES FROM TAFB AND SAB.
VISIBILE...IR...AND MICROWAVE SATELLITE IMAGERY NOW SUGGEST THAT
THE BROAD CIRCULATION CENTER OF DALILA WAS NOT AS FAR WEST AS
EARLIER THOUGHT.
THE NUMERICAL GUIDANCE HAS COME INTO SLIGHTLY BETTER AGREEMENT SINCE
THIS MORNING...BUT DIFFERENCES REMAIN ABOUT HOW A TROUGH TO THE
NORTH OF DALILA WILL INFLUENCE ITS TRACK. A WEAKENING IN THE RIDGE
OVER MEXICO HAS ALLOWED DALILA TO MOVE NORTH DURING THE DAY. THE
CURRENT FORECAST ALLOWS THE NORTHWARD TREND TO CONTINUE FOR ABOUT
12 HOURS OR SO BEFORE STARTING TO CURVE THE STORM TO THE WEST IN A
FASHION SIMILAR TO THE GFS. THE ECMWF AND CANADIAN STILL ALLOW FOR
A MORE NORTHERLY TRACK IN RESPONSE TO AN ANOMALOUSLY STRONG SECOND
SHORTWAVE TROUGH THAT PASSES TO THE NORTH OF DALILA. THE WAY THE
GFS AND GFDL HANDLE THIS SECOND TROUGH IS PREFERRED OVER THE
ECMWF/CANADIAN SOLUTION.
VERTICAL SHEAR IS CURRENTLY AROUND 16 KNOTS OR SO...BUT IT IS
EXPECTED TO DECREASE TO AROUND 5 OT 6 KNOTS IN THE NEXT 24 TO 48
HOURS. GIVEN THE DECREASING SHEAR...WE WOULD EXPECT THE STORM WILL
BE ABLE TO STRENGTHEN TO AROUND 60 KTS BY 36 HOURS. THE STORM
SHOULD WEAKEN AFTER THAT ONCE IT ENCOUNTERS COOLER SEA SURFACE
TEMPERATURES.
FORECAST POSITIONS AND MAX WINDS
INITIAL 24/2100Z 17.3N 110.2W 50 KT
12HR VT 25/0600Z 18.2N 110.7W 55 KT
24HR VT 25/1800Z 19.0N 111.4W 55 KT
36HR VT 26/0600Z 19.8N 112.6W 60 KT
48HR VT 26/1800Z 20.5N 113.8W 55 KT
72HR VT 27/1800Z 21.8N 116.5W 45 KT
96HR VT 28/1800Z 22.8N 119.3W 30 KT
120HR VT 29/1800Z 23.6N 122.1W 20 KT...DISSIPATING
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FORECASTER BANN
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